Ryan Landon, Mike Hast, and Steve Piazza have just published an article entitled "Robust contact modeling using trimmed NURBS surfaces for dynamic simulations of articular contact" in Computer Methods in Applied Mechanics and Engineering 198:2339-2346, 2009.
ScienceDirect - Computer Methods in Applied Mechanics and Engineering : Robust contact modeling usin Contact treatment algorithm for the trimmed NURBS surfaceJournal of Materials Processing Technology, Volume 104, Issue 3, 31 August 2000, Pages 200-206Hyunbo Shim, Euikwon SuhAbstract